do you have the webcam / monitor /keyboard/mouse?
i choose the intel platform because though 2400g will give you better processing power, it's too much trouble since b450 or cheaper boards are not out yet.
16gb should be plenty for office/word documents, it's better to go with more memory than less memory.
the i3 8100 is a very good chip (4 physical core) and should allow you to handle multitask (browsing, office, video calls) quite well.
PCPartPicker part list:
https://pcpartpicker.com/list/TtjM3b
Price breakdown by merchant: https://pcpartpicker.com/list/TtjM3b/by_merchant/
CPU: Intel - Core i3-8100 3.6GHz Quad-Core Processor ($118.62 @ OutletPC)
Motherboard: ASRock - H310M-HDV Micro ATX LGA1151 Motherboard ($56.99 @ SuperBiiz)
Memory: Team - Vulcan 16GB (2 x 8GB) DDR4-2400 Memory ($139.99 @ Newegg)
Storage: Kingston - A400 240GB 2.5" Solid State Drive ($53.83 @ Newegg Marketplace)
Case: Cougar - MX330 ATX Mid Tower Case ($24.99 @ SuperBiiz)
Power Supply: Corsair - CX (2017) 450W 80+ Bronze Certified ATX Power Supply ($23.98 @ Newegg)
Operating System: Microsoft - Windows 10 Home OEM 64-bit ($89.89 @ OutletPC)
Total: $508.29
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-07-10 11:27 EDT-0400